neio Parasitic Copepods on Fish. 83 



rostrum, large, three-jointed, the terminal joint being un- 

 usually long, with oblique curved claw. 



No hamulus detected. 



First maxiUiped of the usual form. Mandible slender, 

 with the last third of the concave border strongly dentate. 

 Palj) short, sharp, slightly curved. 



Second maxilliped: basal joint short and thick, the second 

 a short curved simple claw, bearing a minute hair on the 

 concave border one third from the point ; this means of 

 attachment is peculiarly small compared with that of the strong 

 posterior antenna. Furcula very prominent and strong ; the 

 base is broad, with straight sides, bearing large, divergent, 

 simple branches with blunted ends, the width of the opening 

 being equal to the length of the arms. The first of the 

 swimming-feet {perceopoda) has from the short basal joint a 

 long plumose hair equal in length to that of the second 

 joint ; the third joint or palm bears three short hooked claws 

 on its outer end of about the same length, a fine slender hair 

 at the angle, and three long plumose hairs from the under 

 edge. ISecond perceopod of usual character, the third is 

 peculiar ; the hamulus is distinctly two-jointed, the spur being 

 almost straight, not projecting beyond the border of the first 

 joint of the outer branch ; these two articulate branches are 

 placed close together and are very large, the surface of the 

 terminal joints being finely granular ; the outer bears seven 

 and the inner six plumose hairs. Fourth perceopod of mode- 

 rate size, four-jointed, the three claws of the terminal joint 

 and that of the penultimate being placed close together, of 

 nearly equal lengtli, a fifth being placed higher up ; the last 

 joint of the cephalothorax, from which these spring, is elon- 

 gated and of a diamond shape. 



Genital segment oblong, with a rounded anterior border 

 and strongly lobed posterior angles, from between which rises 

 the extremely elongated abdominal segment; this is biarticu- 

 late, the second joint being very short, its breadth equal to its 

 length, its posterior border giving off two minute sessile 

 caudal plates, which are broader than long ; there are three 

 terminal plumose setae, two minute ones on the outer side, 

 and a single one on the inner. 

 Length 5-6 millim. 



Caligus platytarsisj sp. n. (PI. IV. fig. 2.) 



This animal was obtained in great numbers on a species of 

 Mugil at Muscat, found in the gill-cavity ; only females, more 

 or less mature, were taken. 



